<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>MarkdownLite</title>
</head>
<style>
  .container {
    width: 500px;
    height: 500px;
    border: 1px solid #ddd;
  }
</style>

<body>
  <div id="container" class="container" contenteditable="true">

  </div>
</body>

</html>